The present invention is a pneumatic tube transmission system for transmitting a carrier from an initial terminal to a remote terminal. The invention particularly relates to a transmission system having at least one open terminal and utilizing a slow down blower to create a deceleration zone adjacent the open terminal. The addition of the slow down blower allows the carrier to be pneumatically transmitted from the initial terminal toward the remote open terminal and then decelerated in the deceleration zone, thereby avoiding a high velocity impact between the carrier and the open terminal. The open terminal of the present invention does not require a door, thus allowing the carrier to be removed from the transmission system with a single hand.
Pneumatic transmission systems are widely known and used to transmit articles from one location to another. Typically, the transmission systems consist of tubes or conduits in which a carrier containing documents, samples, or other objects travels by means of pneumatic pressure. The pressure is provided by use of a blower and/or vacuum system. Pneumatic transmission systems are commonly used in drive-in bank tellers where business is conducted via a carrier transmitted between the bank teller and an external terminal in the drive-in area. Pneumatic transmission systems are also used for sending documents between floors and/or offices within the same building, or from one office to another office located some distance apart. Recently, pneumatic transmissions systems have been used by hospitals and clinics for transmitting "fragile cargo" such as blood samples to the laboratory for testing.
In previous pneumatic transmission systems, the carrier would travel through a tube and impact a stop device once it had reached its intended location. In many pneumatic systems, the carrier travels at speeds of 15-20 feet/second or higher, and the impact of the carrier against the stop device can cause great wear on both the carrier and the system. One method for obviating the high velocity impact between the carrier and stop device has employed the use of an air cushion adjacent the receiving terminal. The air cushion is created by pneumatically sealing the receiving terminal and thus creating a trapped column of air which serves to decelerate or "cushion" the carrier. However, such an air cushion system requires that the receiving terminal have a door capable of pneumatically sealing the terminal. The system operator must then manually open the terminal door in order to retrieve the carrier from the system. Alternatively, a complicated mechanism can be provided to automatically open the terminal door upon the arrival of the carrier. However, such mechanisms are often costly and prone to mechanical failures at inopportune times.
Other attempts to resolve the problem of the impact have included the use of other trigger means to shut off the stream of air. These alternative trigger means include such items as a photocell, a timing device, a limit switch, a spring catch, and combinations thereof.
An alternative system in which a carrier is decelerated prior to entering an open terminal area is disclosed in U.S. Pat. No. 4,180,354 to Greene. U.S. Pat. No. 4,180,354 discloses a transmission system in which the pressurized air behind the carrier is routed principally through a check valve positioned near the open terminal to allow the carrier sufficient time to decelerate before discharging into an open terminal. An adjustable gate allows some air to continue to push the carrier to the terminal. A secondary air line adjacent to the open terminal draws in the air from the main transmission line and reroutes it to the blower, thus avoiding the blowing of air through the open terminal. The carrier is decelerated by simply choking off most of the air behind it at a point near the open terminal so that the carrier ejects with a minimum speed from the transmission line into the open terminal.